ARM API Support

[Rémi Forax]

Le 24/06/2010 02:08, Joe Darcy a écrit :
> Greetings
>
> The initial API changes to support the Project Coin feature automatic
> resource management (ARM) blocks have been pushed into JDK 7 [1] and
> will appear in subsequent builds. The corresponding compiler changes to
> support the actual language feature remain in progress.
>
> The initial API work to support ARM was divided into two pieces,
> essential API support and retrofitting platform classes. The essential
> support includes:
>
> * A new interface java.lang.AutoCloseable which defines a single method
>    void close() throws Exception
>
> * A new enum constant in the language model:
>    javax.lang.model.element.ElementKind.RESOURCE_VARIABLE
>
> * Methods on java.lang.Throwable to add and retrieve information about
> suppressed exceptions, including printing out suppressed exceptions in
> stack traces.
>
> The retrofitting includes:
>
> * Having java.io.Closeable extend java.lang.AutoCloseable. (From a
> typing perspective, a subtype of AutoCloseable can be declared to throw
> fewer exceptions than the supertype. Therefore is is fine for the close
> method in AutoCloseable to throw Exception and the close method in
> Closeable to throw the more specific IOException. It would even be fine
> for the close method in a subtype of AutoCloseable to be declared to
> throw no exceptions at all.)
>
> * Adding a close method to java.nio.channels.FileLock and having
> FileLock implement AutoCloseable.
>
> * Adding Closeable as an interface implemented by
> javax.imageio.stream.ImageInputStream.
>
> Other platform classes may be retrofitted to implement AutoCloseable or
> Closable in future builds.
>
> Compared to the API support in earlier versions of the ARM proposal, the
> top-level interface to mark participation in ARM is in package java.lang
> rather than its own package and, after consultation with the JDBC and
> graphics teams, neither java.sql.* nor java.awt.Graphics were
> retrofitted for ARM.
>
> -Joe
>
> [1] http://hg.openjdk.java.net/jdk7/tl/jdk/rev/c4d60bcce958
>      http://hg.openjdk.java.net/jdk7/tl/langtools/rev/be5cafeb318d
>    

There is a bug in printStackTrace(PrintStreamOrWriter)

Set<Throwable> dejaVu = new HashSet<Throwable>();
should be:
Set<Throwable> dejaVu = Collections.newSetFromMap(
new IdentityHashMap<Throwable,Boolean>());

The current code doesn't work as expected if an exception overrides 
Throwable.equals.

Rémi